The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of satellites in orbit. GPS satellites circle the earth in a precise orbit and transmit signal information to earth. GPS receivers take the signal information and use triangulation to calculate the receiver's location. The GPS receiver can compare the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. With distance measured from several satellites, the receiver can determine its position and display it to a user. Once the receiver's position has been determined, a GPS device can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time, and more.
Signals transmitted by a GPS satellite include satellite codes used by GPS receivers. Ideally, the satellite code signals are adjusted to obtain code power fractions, i.e., respective fractions of the signal power used to transmit each code, optimized such that the absolute power level of each code meets GPS standards and the combined codes are transmitted in a constant envelope signal requiring as little power as possible. One method directed to this optimized code multiplexing is channel amplitude optimized constant envelope transmission (CAOCET), as disclosed in U.S. Pat. No. 9,432,110 B2. In the CAOCET method, satellite codes are linearly combined in an in-phase channel and a quadrature-phase channel and then projected onto a unit circle to produce a signal with constant, unit amplitude. However, the projection distorts the original code power fractions. Therefore, a method of code multiplexing that accounts for this distortion could improve GPS satellite code transmission.